Defect Detection Of Pipelines Based On Time-reversal Guided Waves

Pipelines play an important role in the ocean engineering, electricity industry, chemical industry, urban construction and other fields. There are a variety of defects in pipelines that may cause security risk in the long run. Therefore, regular inspection of pipelines is necessary. Ultrasonic guided wave technology features long-distance propagation, time efficiency, and cost effectiveness, and it is promising in inspection of industry pipelines. By means of theoretical analysis, numerical simulation and experimental verification, the time reversal guided wave inspection method is investigated based on cylindrical guided wave theory of hollow cylinders. The researches in this paper are as follows.The finite element method is used to simulate the time reversal guided wave detection of circumferential crack defect and round hole defect. It is shown that the time reversal method can significantly improve the reflection rate of the defect detection signal compared with the direct wave detection method. The interception window width is an important factor that influences inspection capability of the time reversal guided wave method. The variation of reflection rates with circumferential crack depth, circumferential length and radius of the hole type defect are also investigated.The experimental system for pipeline ultrasonic guided wave defect detection based on Labview virtual instrument is established. Experiments validate the conclusion that the time reversal method can significantly improve the defect detection capability. The effect of defect size and circular hole defect is studies with experiments. The variation of reflection rate with circumferential crack depth, circumferential length and radius of the circular hole defect is also studies experimentally.The defect echoes of single and double defects are decomposed and reconstructed using the matching pursuit method based on the excitation waveform. The single defect and double defects can be distinguished by the coefficients of the decomposed atoms. The axial width of single defect and the axial distance of double defects can be reflected by the time interval of atoms.